SIP Sharing
Subject: Endocrine System
Name of test: SHBG Test
Hi people!
Hope you guys had fun so far in your attachment. Well, I am posted to an endocrine research lab that also do some routine lab work. and so yup, I am dealing with hormones. Anyway, there are so many hormones being secreted by our body so it is kind of impossible to focus on all of them.
In this post, I will be focusing on the Sex Hormones-Binding Globulin (SHBG). SHBG is not a hormone but is actually a glycoprotein that is synthesized by the liver. But before I go into SHBG, I will talk about testosterone first.
Testosterone can be present in both males and females and are mainly bound tightly to SHBG. However, they can also be present in the circulation as either the unbound form or weakly bound to albumin and to cortisol-binding globulin. The unbound testosterone and those weakly bound are considered as bioavailable (non-SHBG bound).
Ok. Back to SHBG.SHBG binds to testosterone and 5α-dihydrotesterone with high affinity but to estradiol at a lower affinity. (Estradiol is an estrogen). So, naturally, as females have a higher concentration of estrogen (female sex hormones) than androgen (male sex hormones), SHBG will have a higher concentration in female than in male. And since SHBG mainly binds to testosterone, any changes in the concentration of SHBG can affect the testosterone concentration.
SHBG is usually ordered along with total testosterone in my lab to help measure the bioavailable testosterone in which bioavailable testosterone is the measure of the free circulating testosterone and those that are weakly bound to albumin and cortisol-binding globulin. This is to test for testosterone deficiency in men and in women for excess testosterone production. Measuring only the total testosterone alone does not show testosterone deficiency as you can have high amount of testosterone and high amount of SHBG which actually may results in testosterone deficiency.
Immulite 1000
Picture taken from: http://diagnostics.siemens.com/webapp/wcs/stores/servlet/ProductDisplay?catTree=100001,1015815,1015817&catalogId=-111&langId=-111&productId=172962&storeId=10001
Both the concentration of SHBG and total testosterone can be determined using a machine called Immulite 1000. Basically, everything is automated. So, I just have to load the sample in. =)However, before I can start using the machine, I have to purge the system to remove all bubbles that could be present in the tubing which in turn can affect the exact volume of reagent added. The probe also has to be clean to prevent any contamination. After which, I have to pipette about 120µl of the sample (plasma) into the sample cup. I then load the materials needed in this order: sample cup, dilution cup, leave a space and then the test unit. The machine will then do all the work and I would just have to wait for the results. But, before I can leave the machine alone, I have to make sure that all the samples are "accepted" by the machine. If there are errors detected by the machine, I will then have to troubleshoot.
Anyway, this machine uses assay-specific antibody or antigen-coated plastic beads, alkaline-phosphatase-labelled reagent and a chemiluminescent substrate. The coated bead is contained in an apparatus called the test unit in which it allows all reactions to occur.
The machine will add the sample and the alkaline phosphatise-labelled reagent into the test unit and then incubated. After which, the bead in the test unit are spun at high speed about the vertical axis to remove all unbound antibodies. Using the chemiluminescent substrate, dioxetane substrate, the amount of SHBG can then be quantified by a Photomultiplier Tube.
Picture taken from: http://diagnostics.siemens.com/webapp/wcs/stores/servlet/PSGenericDisplay~q_catalogId~e_-111~a_langId~e_-111~a_pageId~e_79518~a_storeId~e_10001.htm
The reference range is about 13-71 nmol/L for male and 18-114nmol/L for non-pregnant women.
Some indications for abnormal values of SHBG are
Decrease SHBG levels can indicate:
1. Hirsutism - “male-pattern” hair growth in women (found in decrease SHBG in women)
2. Hypothyroidism
3. Androgen administration
Increase SHBG levels can indicate:
1. Hyperthyroidism
2. Hepatic Cirrhosis
3. Pregnancy
Ok. That’s all. Enjoy.
Xin Yi
TG02
posted by THE CODEC 5 @ 12:50 AM
15 Comments:
hey xin yi! hope you're doing great (:
about the order of loading in materials right, you actually have to leave a space? any particular reason for that? and what happens if you unintentionally add lesser or more plasma into the sample cup, will that affect the process?
thanks!
Nurathirah
Tg01
hello xin yi! been a long time since i saw you. hehe
anw, i've got a question. you mentioned there must not be errors right or else you have to do troubleshooting. i wonder if you could tell me what errors you have encountered so far and how you solve the problem. or if there isnt, how would you solve the problems that you might encounter in the process.
thanks! and see you on friday!
Liyanah Zaffre
0607718D
TG02
hello xin yi..
i was attached to a serology lab during my first 2 weeks and i was also given a chance to run samples on the immulite 1000. the exact same machine. heh..
what are the other tests carried out by that machine in your lab? mine only do free-beta HCG, DHEAS and IGF tests..
i usually fill up the sample cup until the 2nd marking of the sample cup for patient samples except for IGF test. IGF requires specific amount of patient sample diluted with pre-treatment solution. do you roughly fill them up into the sample cup or is there a specific amount of diluent or patient sample to add each time?
i was taught to load the sample cup with the patient's sample, followed by the test unit. why does yours have to include the dilution cup and then leave a space before loading the test unit? what difference would it make?
thanks babe C:
nur azeimah
tg02
0607060A
Hi Nurathirah,
Well, the need of leaving a space is because the machine works in this way. Lets say the sample cup is in postition 1, the dilution cup is in position 2, the space is in position 3 and the test unit is in position 4. From what I ovbserved, when the pitpettor wants to pipete the diluted sample to the test unit, it doesnt goes into position 3. Instead, it goes into position 4. Hence, if I didnt leave a space, the diluted sample wont be ablr to be pipetted into the test unit but will be into nothing.
About your second question, if I added lesser plasma into the sample cup, the machine might not be able to detect the presence of the sample and will then reject this "order". If this happens, I will have to add mroe sample into the sample cup and then load them into the machine again. If I have added more plasma, it shouldnt be a problem, just that I have to make sure that the plamsa does not overflow.
Hope that answer your questions. =)
Xin Yi
TG02
Hi Liyanah,
Yup, we haven been seeing each other for a long time. Heard that your lab is very busy. Lol.
Well, so far, I had encountered 3 types of error. By the way, the type of error detected by the machine will be sent to the computer system attached to the machine. So, there isnt a need for me to go investigating for the cause. =)
1st error: insufficient reagent. In this case, I would just need to replace the reagent with a new one.
2ns error: Insufficient sample
This,I would just have to top up with more sample and then load them back to the machine.
Actually, the first time when I did this test, I pipetted 100ul of sample into the sample cup but then I realised that a lot of sample cups were rejected, so I increased the volume to about 120ul.
3rd error: no result
This is because the value is too high. This is case, I will have to redo the test to confirm the result. If its still the same, then I will have to do a manual 2x dilution and then load them back to the machine again.
Yups. That's all.
Xin Yi
TG02
Hi Azeimah,
So far, I have only carry out SHBG test on that machine. This is because most of the time I am doing other stuffs. However, I know that the other test run in our lab using this machine is the total testosterone test. I am not sure if there are still others.
About the amount of sample added, the volume required by the machine is 10ul of the prediluted sample but then the sample cup needs to contain at least 100ul more than the total volume needed. Hence, i added about 120ul to ensure that there is always sufficient volume. So, I guess there is a need of a specific amount of sample added.
And about the need of the dilution cup, it actually depends on the type of assays. In this case, yours does not require dilution but mine needed. The samples for SHBG test are diluted 1-in-21 SHBG diluent automatically by the machine.
And finally about the need for leaving a space, I have answered it in Nurathirah question. So, please refer to it.
Thanks. That's all. Hope that answers your questions.
Xin Yi
TG02
Hello xin yi!!
How long does the Immulite 1000machine runs? What is the incubation period?
Another quest: Are they any quality checks(QC) done on the machine to confirm consistency in the quality of the results?
AmiR
TG02
hi xin yi, nice post u have there, great flow.
i would like to ask, is hypothyrodism very common?
thank you.
raihana
hi xin yi, nice post u have there, great flow.
i would like to ask, is hypothyrodism very common?
thank you.
raihana
Hi Amir,
The Immulite takes about 40 mins before the results can be printed.
As for the incubation time, it depends on the assay. In this case, for SHBG, the incubation time takes 30 mins.
To answer your second question, an adjustor test also commonly known as the calibrators will be carried out every 2 weeks. Controls provided by the test kit will also be run in every test.
Xin Yi
TG02
Hi Raihana,
Thanks for your comment. Anyway, from what I researched, hypothyroidism seems to be occuring 2-5% depending on the study and increase to 15% by the age of 75.
I am not sure if this is counted common but I hope I managed to answer your question.
Xin Yi
TG02
hello xin yi
you displayed the reference ranges for males and non-pregnant women. i would like to know the difference in range for pregnant women compared to the male and non-pregnant women. is there a significant difference?
thanks
rusydiana
Hi Rusydiana,
Ok, from what I have found out, SHBG level tends to start increasing in pregnant women from
the start of conception till about week 30. The concentration can reach to 6-10 times higher than in non-pregnant women. Since healthy male is suppose to have a lower range of SHBG than female. Then, definitely, SHBG in pregnant women will be much higher than in healthy male.
Well, there is a reason for this. You see, when a female gets pregnant, there will be an increase in estrogen. And since estrogen has less affinity to SHBG, the more estrogen in the body will thus lead to a higher concentration of SHBG.
Hope that answer your questions. =)
Xin Yi
TG02
Hello. Sounds like interesting work you are doing =).
Anw, you mentioned that SHBG binds to estradiol (an estrogen) at lower affinity than testosterone. So how does that explain that females have more estrogen than androgen? And why will females have more SHBG than males?
Thanks for the time!
Li Ping
TG 02
Hi Li Ping,
The affinity of SHBG to estradiol or to androgen does not explain why woman has more estrogen than androgen.
By right, women should have more estrogen than androgen. It is the estrogen that develop our female sexual characteristics (and makes us woman) while it is the androgen that develop the male sexual characterisitcs (and makes male man). So, imagine if you have more androgen than estrogen, then you would be more "man".
However, the affinity of SHBG to estradiol does affect the concentration of SHBG in female. When we measure the concentration of SHBG, we are measuring those that are not bound to any hormones. Hence, since SHBG has lesser affinity to estradiol, it is more likely that most SHBG will be unbound and thus a higher concentration. As in the case for man, since SHBG has a higher affinity for androgen, most SHBG by right should be bound to them and hence lesser unbound SHBG. Thus, a lower SHBG concentration.
Well, hope my answer is clear.
Thanks.
Xin Yi
TG02
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